Hi, a scarf and a muffler are two different things here in Japan. People wear mufflers only when the weather is (very) cold, and scarfs are too thin to keep your neck warm in winter. I've checked some English dictionaries, including the ones on WR, and a couple of dicitonaries I have suggest that the term 'muffler' is just an old-fashioned version of 'scarf'. One example is Collins Cobuild for Advanced Learner's English Dictionary, which says "A muffler is the same as a scarf [OLD-FASHIONED]". Also, a book written by a British writer about British English I have says that Brits use "scarf" and Americans use "muffler". Is this true? If someone whose birthday is in the beginning of autum, for example, said to you that he/she wanted a scarf, or muffler, for their birthday, would you have to ask, "You want the thick one for the winter, or the thinner one?"